The development of edema in congestive cardiac failure involves the retention or salt and water. The work carried out in the first part of this granting period has demonstrated that there is a primary increase in water intake which contributes to the development of edema. In addition, there is an increase in vasopressin secretion and thus water retention. The goal of the proposed work in the third year of the grant is to evaluate the role of the renin/angiotensin system in the stimulation of drinking and vasopressin secretion in heart failure. The experiments will be carried out on a population of trained dogs. The dogs will be subjected to thoracic caval constriction, an experimental model of low output failure. Effects of angiotensin II will be evaluated by the use of blocking drugs, such as saralasin, administered directly into the third ventricle. the effects of alterations in water intake and salt intake on the edema, hormone levels and cardiac performance will be evaluated. These studies should aid in the understanding of congestive cardiac failure in human disease.